Hahahha. So you think the sibling just died on its own? It clearly killed it, if you read between the lines. Hence why they call the Indominus a killing machine. Killing for sport. Of course it killed the sibling.
"Though they do hunt for food, one known I. rex was shown to kill mainly for sport. This individual also was known to have committed cannibalism, as she killed and ate her own sibling, which was the first thing she did as soon as she hatched".
No, I'm not saying it died on its own, I'm just saying that its cause of death is unknown. Which it is. It might be somewhat implied she actively killed her, but because it never got proven it cannot be treated as a fact. Fact.
Killing machine is just an exaggeration to describe something being a fierce and effective fighter, sometimes also to describe something lacking empathy in fight. The word does not have to be meant literally.
Masrani: "Say, I thought there were two of them?"
Claire: "There was a sibling in case this one didn't survive infancy."
Masrani: "Where's the sibling?"
Claire: "She ate it."
There you got it, quoted from the movie, they did even expect that one of the siblings might die by natural reasons, not surviving infancy. Thus it is very much possible that it just died shortly after eclosion or later because it was too weak, sick or whatever and then got eaten by her sister.
Regarding "KiLliNg fOr SpOrT", Owen and Claire just saw the result of the Indominus' attack on the Apatosaurus herd. We don't know whether she really felt like "oh, killing is fun" or just instincts overtook her, similar to sharks falling into bloodlust. Or house cats killing prey like mice but not eating them. We - don't - know.
The text in JWE isn't a very good one because it portrays assumptions as facts. It's not like we don't know whether she killed her sibling at all, we have even less knowledge about WHEN she could've killed her. It could've happened right after eclosion, it could've happened after two days, a week, a month, a bloody year. WE. DON'T. KNOW. The InGen data base in JWE has no proof or source to what it is stating as facts.
Your "argumentation" is based upon a bunch of assumptions. Prove me wrong.